Macabuhay, A., Houshmandfar, A.,
Nuttall, J., Fitzgerald, G.J., Tausz, M.
and Tausz-Posch, S.
2018
"Can elevated CO2 buffer the effects
of heat waves on wheat in a
dryland cropping system? "
Environmental and Experimental Botany
155: 578-588
SUMMARY:
Grain yield increases
due to elevated CO2
under control conditions
was +25.1% and +54.0%
in 2013 and 2014,
respectively.
Temperature stress
from heat waves
reduced this yield
stimulation to
+14.6% in 2013,
but maintained it
at +55% in 2014.
Atmospheric CO2 enrichment
positively impacts wheat growth
and yield, even when growing
conditions are less than ideal.
Very high (7-15°C above normal air)
temperatures reduced those benefits
in one year (though the CO2 impacts
was still positive), but maintained them
in another year.
DETAILS:
Heat stress during key periods
of the growing season has
the potential to reduce crop yields.
Climate models forecast
increased heat waves
in the future.
So Macabuhay et al. (2018)
investigated the effects
of short-term (3-day)
heat waves on wheat growth.
Their work was at the Australian
Grains Free Air CO2 Enrichment
facility in Horsham, Victoria,
Australia, located in the
semi-arid cropping region
of south-eastern Australia's
wheat belt.
In both 2013 and 2014,
the authors grew wheat
(Triticum aestivum, cv. Yitpi)
under two atmospheric CO2
concentrations
( ~390 ppm for ambient
and ~550 ppm for elevated )
and then subjected portions
of the crops to one of three
simulated heat waves
at different stages of the
growing season.
The first heat wave was initiated
on a subset of crops 5 days before
anthesis (HT1), the second at
15 days post-anthesis (HT2)
and the third at 30 days
post-anthesis (HT3).
Temperatures during the
simulated heat waves
averaged between 7 and 15°C
above the normal (ambient)
outside air temperature.
The 2013 growing season
was relatively wet,
requiring no supplemental
irrigation,
but the 2014 season
was relatively dry and
required irrigation
to keep the crops alive.
For biomass, elevated CO2
increased aboveground biomass
under control conditions
(i.e., no heat wave applied)
by +23.2% in 2013.
This CO2-induced stimulation
was reduced to +11.7%
when averaged over
that reported for plants
subjected to the three
simulated heat waves.
In 2014, the drier year
of the study,
aboveground biomass rose
by a much larger +71.4%
in response to elevated CO2
under control conditions.
And that percentage
stimulation was maintained
under drought conditions,
where the average
aboveground biomass
increase of plants
in the three simulated
heat wave treatments
amounted to +69.1%.
